Fuel cells have been attracting considerable attention in recent years as examples of electrical cells that offer superior environmental friendliness and a high level of efficiency. In a fuel cell, generally, an oxidizing gas such as the oxygen within air is subjected to an electrochemical reaction with a fuel gas such as hydrogen, thereby generating electrical energy. Water is generated as a result of the electrochemical reaction between the hydrogen and oxygen.
Different types of fuel cells include phosphoric acid fuel cells, molten carbonate fuel cells, solid electrolyte fuel cells, alkali fuel cells, and solid polymer fuel cells. Of these, solid polymer fuel cells, which offer certain advantages such as ambient temperature startup and a rapid startup time, are attracting particular attention. This type of solid polymer fuel cell can be used as the power source for a moving object such as a vehicle.
A solid polymer fuel cell is assembled by laminating together a plurality of unit cells, a current collector and an end plate and the like. Each unit cell for the fuel cell comprises an electrolyte membrane, a catalyst layer, a gas diffusion layer and a separator. The fuel cell separator is manufactured by machining a metal material or carbon material or the like.
Patent Document 1 discloses a gold-plated structure having gold-plated sections and non-plated sections on the surface of a titanium substrate, wherein the gold-plated sections are scattered across the surface of the titanium substrate in the form of islands having a diameter of not more than 100 nm but not less than 1 nm, and also discloses a fuel cell separator formed from this gold-plated structure.
Patent Document 2 discloses a fuel cell separator in which the surface of a stainless steel sheet that has undergone no surface preparation treatment is coated with gold at a surface area ratio of 2.3 to 94%.